1. Field of the Invention
The present invention relates to an AC generator for a vehicle and, particularly, to an AC generator which has a device for limiting the rotation speed thereof.
2. Description of the Related Art
An AC generator disclosed in JP-A-9-107697 is provided with auxiliary permanent magnets between pole pieces in addition to a field coil so that a minimum output current can be generated even when the field coil is not energized. This AC generator has to have a bridge circuit composed of four switching element to increase the field current at lower rotation speeds and reduces the same at higher rotation speeds. However, this kind of bridge circuit is comparatively expensive and generates considerable heat. Accordingly, it is difficult to provide a compact AC generator having such a bridge circuit therein.